Electron beam scanning device



Oct. 29, 1968 D. E. HULTBERG ETAL 3,408,532

ELECTRON BEAM SCANNING DEVICE 4 Sheets-Sheet 1 Filed Dec. 6, 1965 DYNODE CONTROL ADDRESSING LOGIC CONTROL SIGNAL SOURCE INVENTORS LTBERG DONALD E. HU LE5TER A- SEFFR\ES ATTORNEY 1968 D. E. HULTBERG ETAL 3,408,532

ELECTRON BEAM SCANNING DEVICE Filed Dec. 6, 1965 4 Sheets-Sheet 2 INVENTORS DONALD E. HULTBERG LYESTER A. IEFFRIES /QJW' ATTORNEY 1968 D. E. HULTBERG ETAL 3,403,532

ELECTRON BEAM SCANNING DEVICE Filed Dec. 6, 1965 4 Sheets-Sheet 3 33 IIIIIKIIIII W I +M {z ADDRESSING LOGIC FIE- IE- 1N CONTROL DONALD E. Hd g s SIGNAL LESTER A. JEFFF2\ES SOURCE ATTORNEY United States This invention relates to an electron beam scanning device, and more particularly to such a device which is operative in response to a digital control signal and is capable of random addressing.

Electron beam scanning is used extensively in cathode ray devices for applications such as video camera tubes, video display tubes such as television picture tubes, and memory and storage tubes. These cathode ray scanning devices of the prior art have several shortcomings. Firstly, a rather bulky elongated configuration is required to accommodate the electron gun and deflection system inherent to this type of device. The dimensions of such structure are particularly cumbersome where relatively large display screens are involved. Efforts to minimize the dimensions of such structure often result in a severe sacrifice of the linearity and definition of the display. Further, such devices are readily subject to .ambient electrostatic and electromagnetic fields which can impair the linearity and focus. Also, such cathode ray tube devices are adapted to scan in a relatively cyclical fashion and cannot randomly be addressed to any point on the target without sacrificing resolution and speed of operation. This somewhat impairs the efficiency of their operation in response to randomly addressed inputs such as might be involved in a memory or storage tube or a specialized display application.

While efforts have been made in the prior art to provide a digitally responsive display system capable of random addressing, such systems have been unable to provide either the compact structure, speed of operation, defini tion, or the brightness of display to be desired. Further, many of these systems require extensive auxiliary control systems for providing the addressing operations.

The device of this invention overcomes the shortcomings of prior art devices in providing a relatively fiat thin electron beam scanning device capable of high lineearity and definition which ambient electrostatic and electromagnetic fields. The device of the invention utilizes electron multiplication techniques which assure adequate electron current at the target for proper operation. Further, the deivce of the invention operates in response to a digital control signal and is capable of random addressing as well as regular scanning.

The devcie of the invention achieves the desired end results by utilizing a plurality of coded .dynode members which are sandwiched between an electron emitting cathode and a target plate. Each dynode has a plurality of apertures formed therein which are effectively aligned with corresponding apertures on all the other dynodes. The dynode aperture portions each have electron multiplying surfaces therein for multiplying the electrons in the electron beam by secondary emission techniques. The dynodes further each have a pair of seaparate conductive portions thereon forming fingers, each conductive portion being electrically insulated from its paired portion is relatively unaffected by F phor coating 15.

3,408,532 Patented Oct. 29, 1968 and such conductive portions being arranged in a predetermined coded finger configuration. Digital control means are connected to the conductive portions of each dynode to excite one of each pair thereof with a potential such as to accelerate the flow of electrons from the cathode to the target and the other of each pair with a potential such as to retard'the flow of electrons. The digital control means operates in response to addressing logic. By this technique, any oneelement of the target as defined by the aligned dynode hole portions can be excited at any one time in response to various digitally controlled excitation inputs to the dynodes.

It is therefore an object of this invention to provide an improved electron beam scanning device.

It is a further object of this invention to provide an electron beam scanning device of relatively fiat and compact construction.

It is still another object of this invention to provide an electron beam scanning device having high linearity and which is relatively insensitive to ambient electrostatic and electromagnetic fields.

It is still a further object of this invention to provide an electron beam scanning device directly operable in response to a digital control signal which is capable of random addressing.

It is still another object of this invention to provide an electron beam scanning device in which the amplitude of the scanning beam is supplemented by electron multiplication techniques.

Itis still another object of this invention to provide an electron beam scanning device capable of utilization as an image display, memory device, or image sensing device.

Other objects of thisinvention will become apparent from the following description taken in connection with the accompanying drawings, of which- FIG. 1 is a schematic drawing illustrating the operation of one embodiment of the device of the invention,

FIG. 2 is a perspective drawing illustrating the general structure of an embodiment of the device of the invention,

FIG. 3 is a schematic drawing illustrating dynode coding which may be utilized in one embodiment of the device of the invention,

FIG. 4 is an elevational cross sectional view illustrating the structure of one embodiment of the device of the invention,

FIG. 5 is an elevational cut-away view illustrating how electron multiplication is achieved in the embodiment of the device of the invention illustrated in FIG. 4, and

FIG. 6 is a schematic drawing illustrating the operation of the digital control circuitry utilized in the embodiment of the device of the invention of FIGS. 4 and 5.

Referring now to FIG. 2, one embodiment of the device of the invention is illustrated. This particular embodiment, for illustrative purposes, is shown as a display device. It can be readily appreciated, however, that the same general construction can be utilized for an image sensor or a memory tube by appropriate modifications within the purview of those skilled in the art. A casing is formed by image plate 11, back plate 12 and frame 14 which are joined together in air tight relationhsip and the enclosed space evacuated to provide a vacuum environment. On the inner surface of image plate 11 is a phos- Back plate 12 has an electron emissive cathode 16 mounted thereon. Cathode 16 is preferably of the cold cathode type and may have a radio-active or photo emissive surface which is suitable for providing an adequate electron current.

Sandwiched between cathode 16 and plate 11 are a control grid member 19 and a plurality of dynode m mbers 20-25. Each of these dynode members, as to be explained fully further on in the specification, includes a pair of oppositely positioned conductive sections which are formed on an insulating member. A plurality of electron beam directing apertures are formed in the dynode members. The various power and control signals are fed to the various dynodes, the grid and the cathode and phosphor target through electrical receptacle 30.

Referring now to FIG. 1, the general operation of the device of the invention is illustrated. An electron accelerating potential supplied by DC power source 33 is applied between phosphor target and cathode 1. Various graduated potentials between the target potential and the cathode potential are supplied to dynode control 32 from voltage divider 35. As to be explained in detail in connection with FIG. 6, dynode control 32 supplies an electron beam accelerating potential to half of the conductive portions of each of dynodes -25, and an electron beam repelling potential to the other half of the conductive portions of each of the dynodes. Thus, at any one time half of the control area of each dynode is repelling the electron beam while the other half of the control area of each dynode is accelerating the beam. The dynode accelerating and repelling conditions at any particular time are controlled in response to addressing logic 40 which actuates dynode control 32 in response to a control signal source 41. Thus, control signal source 41 may cause dynode control 32 to effect a raster scanning pattern on target 15 such that a video image 42 is generated in response to video signals fed to control grid 19 from a video signal source 45. It is to be noted, that while a device for showing a conventional video display is shown in FIG. 1 for illustrative purposes, that dynode control 32 can also be made to operate in response to a random addressing input which will excite any portion of target 15 directly without passing through adjacent portions of the target, i.e., the beam can be shifted from one side of the screen to the other without passing through any of the intermediary points. This will become apparent as the description proceeds.

Referring now to FIG. 3, an exploded schematic dr-awing is shown illustrating the operation of one embodiment of the device of the invention. Positioned between electron emitting cathode 16 and target 15 is a control grid 19 and a plurality of dynode members 20-25. Grid 19 and each of dynode members 20-25 has a series of apertures 47 formed therein, each aperture on the control grid and each dynode being substantially aligned with an associated aperture on each of the other dynodes. Dynode 20 has a first electrically conductive portion 20a covering substantially half of its broad surface area, and a second electrically conductive portion 2% covering substantially the other half of such broad surface area, such conductive portions being electrically insulated from each other and connected to opposite outputs of flipflop 48. Thus, when conductive portion 20a is receiving one potential output of flipflop 48, conductive portion 20b is receiving the other potential output thereof, and vice versa. Dynodes 21-25 have paired conductive portions 21a-25a and 21b-2Sb, which are insulated from each other similarly to sections 20a and 20b and operate in the same fashion in response to flipfiops 49-53 respectively.

Each of the dynode conductive portions covers substantially one half the broad surface area of its associated dynode but such portions are arranged in different finger patterns, such that by proper actuation of flipflops 48-53 an electron beam can be made to pass from cathode 16 through to target 15 through only one selected set of aligned apertures 47 at any one time. Such operation is 4 illustrated in FIG. 3 for a combination of fiipfiop actuations whereby dynode sections 20a-25a have an electron beam accelerating potential thereon and whereby dynode portions 20b-25b (indicated by stippling) have an electron beam repelling potential thereon. For the example shown in FIG. 3, it can be seen that the beam represented by the line 60 is the only one that can pass all the way through to the target. All other beams, such as for example that indicated by the line 61, are prevented from passage by a repelling potential (in this instance provided by dynode portion 23b) somewhere along their respective paths. Thus, it can be seen that by various combined actuations of flipfiops 48-53 in response to gating control signals, various scanning patterns for either regular scanning or random addressing of the target can be achieved. As to be explained further on in the specification, the beam current is amplified appreciably by electron multiplication techniques to assure sufficient beam current at the target.

Referring now to FIGS. 4 and 5, the structural features of one embodiment of the device of the invention are shown. The entire unit is housed in a vacuum tight hous ing formed by plates 11 and 12 and frame 14. Cathode 16 may be fabricated of electrically conductive material that has been sufficiently radio activated to cause electron emission therefrom at ambient temperatures. If so desired, other types of cathodes such as those of the thermonic or photo-emissive type may also be utilized. Control grid 19 and dynodes 20-25 each comprises a plate 65 of a nonconductive material, such as glass, having thin metallic coatings 19a-25a and 20b-25b respectively on opposite sides thereof. Such metallic coatings are arranged in accordance with patterns such as indicated in FIG. 3 to provide a desired coding. It should be noted, of course, as shown in FIG. 3, that the control grid 19 has allover metallic coatings on both sides thereof and hence can be used for intensity modulation of the beam.

Target 15 is formed by a phosphorescent coating on the inner surface of plate 11. It is to be noted, of course, that any suitable insulating material may be utilized in lieu of glass for plates 65. The cathode, the control grid and the various dynodes are separated from each other by means of insulator strips 70, the strips and the various units being joined together to form an integral unit by any suitable means such as cementing. Apertures 47 which are formed in plate members 65 are angulated with respect to the horizontal to form a zigzag pattern. It has been found that the use of such a zigzag pattern enhances the electron multiplication by providing a greater incidence of electrons against the sides of the channels. The sides of apertures 47 are coated with a coating of a material such as lead oxide or tin oxide, which will provide good secondary electron emission with the impingement of electrons thereon. In an operative embodiment of the device of the invention, it has been found that good results can be achieved with apertures having a length which is five times their width.

Referring now particularly to FIG. 5, the electron multiplication achieved in the device of the invention is illustrated. Single line illustrates an initial incoming electron impinging against coating 75. As can be seen, the impingement of this electron causes the emission of two electrons. This electron multiplication process is repeated as the beam proceeds, until, as can be seen, a fairly large number of electrons are generated. The electron current by virtue of the secondary emission process is greatly multiplied for each electron emitted from the cathode. It is to be noted that more (or in some instances even less) than two electrons can be generated by secondary emission in any instance and the binary multiplication process shown is merely illustrative of how secondary emission accomplishes an increase in the electron current. As can be seen, the electrons 83 are repelled by dynode portions 2212 which have a repelling potential therebetween and thus never pass through to the target.

Referring now to FIG. 6, an embodiment of a scanning control that may be utilized in the device of the invention is shown. For the convenience of illustration, only three of the flipflops and one of the dynodes are shown, this in view of the fact that all of the other flipflops and dynodes are operated in the same fashion.

Flipfiops 48, 49 and 53 are energized by means of power sources 90, 91 and 92 respectively. Each such power source, however, is referenced at a different potential point along voltage divider 35 which receives the potential of power source 33 thereacross. Flipflops 48, 49 and 53 are acutated in response to the output of addressing logic 40, which in turn is controlled by control signal source 41. At any one time either one or the other of the fiipflop stages of each of flipflops 48, 49 and 53 is conductive, While the other is at cutoff.

The collector of fiipflop stage 48a is connected to the top section of conductive portion 20a, and the bottom section of conductive portion 20b, while the collector of fiipflop stage 48b is connected to the top section of conductive portion 20a. Thus, for example, when fiipflop stage 48a is conductive and stage 481) non-conductive, the top section of conductive portion 20a will have a positive potential with respect to the bottom section thereof, while the bottom section of conductive portion 20b will have a positive potential with respect to the top section thereof. When the fiipflop reverses such that section 48b becomes conductive and section 48a becomes non-conductive, an opposite polarity condition will be presented to the dynode portions. The potential of power sources 90-92 is made suflicient to produce an adequate repelling signal to the electron beam (e.-g. of the order of 200 volts). While a single high voltage repelling signal can be used for all the dynodes, the use of separate incremental potential gradients, as shown and described in connection with FIG. 6, greatly alleviates dynode fashion the flipflops are utilized at the various dynodes to control the electron beam. As already noted, each of the flipfiops is used in the same fashion as described for fiipflop 48 and dynode 20 for the control of their respective dynodes.

Thus, with a relatively small number of flipflops, complete random addressing control can be achieved in the device of the invention. Of course, as the number of dynode stages is increased, the size of the individual apertures can be decreased and thus the definition of the device improved. While the intensity of the electron beam would normally tend to decrease with the number of dynodes, this problem is obviated by virtue of the electron multiplication achieved in the device of the invention which proportionately compensates for the diminution of the electron beam intensity as the number of control apertures and dynodes are increased. It is to be noted that very good focusing and linearity is achieved in the device of the invention by virtue of the utilization of alined apertures in controlling the electron beam. Thus, such beam is tightly controlled through its entire path, and is not subject to ambient disturbances.

While for illustrative purposes the dynode pattern arrangement has been illustrated and described for a natural binary coding, other types of coding such as, for example, GRAY coding can also be used and may in some instances provide certain advantages.

The device of the invention thus provides means for replacing bulky cathode ray tube equipment with a relatively fiat scanner which has the advantages of being operative in response to digital control signals and capable of random addressing.

While the device of the invention has been described and illustrated in detail it is to be clearly understood that this is intended by way of illustration and example only, and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the following claims.

We claim:

1. An electron beam scanning device comprising a gas evacuated sealed casing member insulation problems. In this an electron source mounted within said casing member,

a target member mounted within said casing member opposite said electron source,

a power source connected between said target member and said electron source for providing an electron accelerating potential therebetween,

a plurality of dynode member sandwiched between said electron source and said target member for controlling the flow of electrons therebetween,

said electron source, said target member and said dynode member being alined opposite each other,

said dynode members each having a plurality of conductive coded finger portions which are insulated from each other,

said dynode members further each having a plurality of aperture means formed therein for channeling the flow of electrons between said electron source and said target member, and

control means for selectively applying an electron accelerating potential to at least one of the finger portions of each of said dynode members and an electron repelling potential to the others of the finger portions of each of said dynode members,

whereby said dynode members cause an electron beam from said electron source to said target member to be addressed in response to said control means.

2. The device as recited in claim 1 wherein said target member, said electron source and said dynode members are substantially flat and are alined with their broad surfaces opposite each other.

3. The device as recited in claim 2 wherein said aperture means are distributed over the broad surface area of said dynode members with each dynode member aperture means being alined with corresponding aperture means on each of the others of said dynode members.

4. The device as recited in claim 1 wherein the portions of said dynode members forming said aperture means have electron multiplying surfaces.

5. The device as recited in claim 1 wherein said dynode members have similar finger portions on the opposite broad surfaces thereof, said control means including means for alternatively applying a potential in one polarity or a polarity opposite said one polarity between oppositely positioned finger portions.

6. The device as recited in claim 2 wherein said electron source comprises a radioactive cathode.

7. An electron beam scanning device comprising a gas evacuated sealed casing means,

a substantially flat cathode member mounted within said casing means,

a substantially flat target member mounted within said casing means opposite said cathode member,

a power source connected between said target and cathode members for providing an electron accelerating electron field therebetween,

a plurality of substantially fiat dynode members sandwiched between said cathode and target members for controlling the flow of electrons therebetween,

said cathode, target and dynode members being alined with their broad surfaces opposite each other,

said dynode members each having a plurality of conductive coded finger portions on at least one of the broad surfaces thereof which are insulated from each other,

said dynode members further each having a plurality of apertures formed therein running from one broad surface to the opposite broad surface thereof and distributed over the broad surface area thereof, the apertures of each of said dynode members being alined with corresponding apertures on each of the others of said dynode members, and

control means for selectively applying an electron accelerating potential to at least one of the finger portions of each of said dynode members and an 7 electron retarding potential to the others of the finger portions of each of said dynode members, whereby said dynode members cause an electron beam to pass from said cathode member to said target member through only one set of said alined apertures at a time in response to said control means.

8. The device as recited in claim 7 wherein said alined dynode apertures are arranged in a zigzag pattern.

9. The device as reicited in claim 7 wherein the portions of said dynodes forming said apertures have electron multiplying surfaces.

10. The device as recited in claim 7 wherein each finger portion comprises two similar finger sections 10- 8 cated opposite each other on the opposite broad surfaces of said dynode members.

11. The device as recited in claim 7 wherein said control means includes a plurality of flip-flops, the outputs of each of said flip-flops being connected to'oppositely drive the finger portions of an associated one of said dynode members, and addressing logic means for actuating said flip-flops.

No references cited.

RODNEY D. BENNETT, Primary Examiner. c; E. WANDS, Assistant Examiner. 

1. AN ELECTRON BEAM SCANNING DEVICE COMPRISING A GAS EVACUATED SEALED CASING MEMBER, AN ELECTRON SOURCE MOUNTED WITHIN SAID CASING MEMBER, A TARGET MEMBER MOUNTED WITHIN SAID CASING MEMBER OPPOSITE SAID ELECTRON SOURCE, A POWER SOURCE CONNECTED BETWEEN SAID TARGET MEMBER AND SAID ELECTRON SOURCE FOR PROVIDING AN ELECTRON ACCELERATING POTENTIAL THEREBETWEEN, A PLURALITY OF DYNODE MEMBER SANDWICHED BETWEEN SAID ELECTRON SOURCE AND SAID TARGET MEMBER FOR CONTROLLING THE FLOW OF ELECTRONS THEREBETWEEN, SAID ELECTRON SOURCE, SAID TARGET MEMBER AND SAID DYNODE MEMBER BEING ALINED OPPOSITE EACH OTHER, SAID DYNODE MEMBERS EACH HAVING A PLURALITY OF CONDUCTIVE CODED FINGER PORTIONS WHICH ARE INSULATED FROM EACH OTHER, SAID DYNODE MEMERS FURTHER EACH HAVING A PLURALITY OF APERTURE MEANS FORMED THEREIN FOR CHANNELING THE FLOW OF ELECTRONS BETWEEN SAID ELECTRON SOURCE AND SAID TARGET MEMBER, AND CONTROL MEANS OR SELECTIVELY APPLYING AN ELECTRON ACCELERATING POTENTIAL TO AT LEAST ONE OF THE FINGER PORTIONS OF EACH OF SAID DYNODE MEMBERS AND AN ELECTRON REPELLING POTENTIAL TO THE OTHERS OF THE FINGER PORTIONS OF EACH OF SAID DYNODE MEMBERS, WHEREBY SAID DYNODE MEMBERS CAUSE AN ELECTRON BEAM FROM SAID ELECTRON SOURCE TO SAID TARGET MEMBER TO BE ADDRESSED IN RESPONSE TO SAID CONTROL MEANS. 